CN106329911A - VCC voltage detection-based three-terminal constant current control framework of switching power supply - Google Patents
VCC voltage detection-based three-terminal constant current control framework of switching power supply Download PDFInfo
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- CN106329911A CN106329911A CN201510411484.3A CN201510411484A CN106329911A CN 106329911 A CN106329911 A CN 106329911A CN 201510411484 A CN201510411484 A CN 201510411484A CN 106329911 A CN106329911 A CN 106329911A
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Abstract
The invention provides a VCC voltage detection-based three-terminal constant current control framework of a switching power supply, and belongs to an inductor current control technology of the switching power supply. Voltage drop at two ends of an inductance detection resistor is indirectly detected by using a constant current control unit, and the maximum value of the voltage drop is limited through a comparator, thereby achieving the target of controlling inductor current. The invention further provides a method for judging a valley bottom by detecting drain terminal voltage.
Description
Technical field
The invention belongs to a kind of Switching Power Supply control method, a kind of VCC of utilization voltage is to detect a kind of Switching Power Supply current constant control technology of inductive current, its other key character is, control port number altogether only has three, is power port VCC, chip ground CS, high pressure drain terminal D respectively.
Background technology
Switching Power Supply is because its energy conversion efficiency is high, it is easy to control, in LED constant current control system, in occupation of the status of main flow.If Fig. 1 is common non-isolation type buck topology structure (BUCK), K0 is main inductance, and K1 is auxiliary winding.The output voltage of K1 receives the feedback detection foot FB foot of chip by the dividing potential drop of R4, R5.The CS foot of chip receives ground by R3 resistance, for detecting peak point current when internal power metal-oxide-semiconductor is opened.VCC is power supply foot, for providing the running voltage of whole chip；VIN voltage passes through supplying resistance R2 to VCC capacitances to supply power.D end is connected on the junction of D1 and K0, is connected on current detecting end, i.e. CS end at chip internal by power MOS pipe.D1 is fly-wheel diode, chip internal switching tube is closed when, provides current path to inductance K0.I5, I6, I7 are LED lamp bead, and the number of this lamp bead is only limited (because being buck configuration, the total voltage of lamp bead is not above input voltage) by input voltage in principle.C3 is output capacitance, for reducing the current ripples of output.
As in figure 2 it is shown, be its internal control circuit.VCC foot is connected to the input of in-line power module I 44, and I44 output 5V power supply gives the running voltage that the offer of other module is stable.FB foot keeps I46 and demagnetization detection I47 to be connected to the set end of rest-set flip-flop I41 by sampling.CS end is connected to the positive input terminal of comparator I43, and what negative input end connected is to compare threshold value VTH.The output of comparator I43 is connected to the reset terminal of rest-set flip-flop I41.The output of rest-set flip-flop I41 connects the control end of switching tube M0, controls being turned on and off of switching tube.Its operation principle is such that when switching tube M0 turns on, and D terminal voltage pulled down to earth potential, and inductance K3 other end voltage is that input voltage deducts output voltage, and inductance is under the effect of this voltage, and electric current persistently increases.Meanwhile, CS pin voltage increases the most accordingly.When this voltage increases to threshold value VTH, comparator I43 exports reset signal, is resetted by rest-set flip-flop, and M0 is closed.Correspondingly, D terminal voltage will gradually rise, and when this voltage is increased to deduct output voltage equal to input voltage, inductance K3 enters demagnetized state, and inductive current starts to reduce.Final D terminal voltage is than input voltage during a high diode voltage, and D6 turns on, and K3 electric current persistently will reduce with fixing speed.The state of inductance K3 is reflected on FB pin by auxiliary winding K4 and R19, R18, and is kept I46 and demagnetization detection I47 to read and process by chip internal sample.When inductive current is reduced to zero, I47 exports set signal, and rest-set flip-flop is set to 1, and switching tube M0 is opened.Inductance K3 enters charging-discharging cycle next time.
This control structure is current common structure, and it has some obvious shortcomings: first is, needs feedback detection foot, namely FB foot；It then becomes necessary to there is auxiliary winding K4, such two coil configuration so that the cost of system is high, and power volume is big.Second is, detection foot FB is more sensitive for feedback, the most affected by noise.3rd is, the control port of chip is the most, needs to use S08 encapsulation, or DIP8 encapsulation, and therefore cost is high.4th is, the element of system is the most, and peripheral complicated, reliability is low.
Fig. 3 is the framework improved, and have employed the structure of high-end floating, and its advantage is to eliminate auxiliary winding, reduces cost.R9 and R10 is serially connected, and it is connected across inductance L1 two ends, resistance R10, R9 junction is connected on FB foot, for detecting output voltage: when the switching tube within I13 is closed, the when of diode D3 conducting, D3, R8, L1, I14 form loop, and now the voltage at L1 two ends is just approximately equal to the voltage at LED lamp bead string I14 two ends, and such FB foot just can detect the working condition of L1 and I14.Although Fig. 3 improves Fig. 1 needs the drawback of twin coil, but still has following shortcoming: first is, still there is the FB foot of sensitivity；Second is, the original paper of system still compares many；3rd is, the number of pins of control chip does not the most reduce.
Summary of the invention
It is an object of the invention to design a kind of beneficially Switching Power Supply current constant control technology highly integrated, to insensitive for noise.Particularly, this control technology makes the control port of needs minimum, and peripheral cell is minimum, it is not necessary to auxiliary winding, it is not required that feedback detection foot；Can also reliably detect simultaneously and control to flow through the electric current of LED lamp bead, it is achieved high integration, in high precision, the LED constant current of high reliability controls.It is mainly characterized by, and by signal detection resistance, LED current is modulated on VCC DC voltage, and LED current is separated from VCC signal by sampling hold circuit and differential detection circuit.To reach detection and to control the purpose of LED current.Its another obvious characteristic is, by sampling, holding, difference and the calculating of drain terminal signal, in the case of without auxiliary winding, it is achieved the lowest point is opened, to reduce the loss of Switching Power Supply.
According to technical scheme, described Switching Power Supply current constant control technology, including reality power management and the power stage of conversion, detection resistance for inductive current detection, VCC electric capacity for Signal averaging and modulation, with constant-current control unit based on VCC voltage detecting (hereinafter referred to as " constant-current control unit "), and control switching tube conducting the lowest point sampling and computing unit (hereinafter referred to as " the lowest point computing unit ").When detecting resistance and flowing through electric current, the voltage signal at detection resistance two ends is just modulated on VCC electric capacity as difference component, this signal will be sampled by constant-current control unit, and carry out Difference Calculation with instantaneous value, restore the differential voltage at detection resistance two ends, when this differential signal is more than threshold value VTH, constant-current control unit will produce reset signal, close power tube.Control within setting value with this inductive current.
Described power stage includes power switch, inductance and one or more light emitting diodes being sequentially connected with, also include and light emitting diode and the fly-wheel diode of inductance reverse parallel connection, one end of described inductance and the drain terminal of power switch connect, and the other end and light emitting diode connect.Described detection resistance one end be systematically connected, be connected one end and chip.Induction charging electric current flows through detection resistance, and the voltage of the VCC port seen in chip is equal to the pressure drop at VCC electric capacity two ends and the difference of detection resistance two ends pressure drop.Inductive current can be obtained by detection resistance drop, and the pressure drop detecting resistance can be obtained by VCC port voltage.Described constant-current control unit includes, sampling holding, difference and unit gain, comparator and latch.Constant-current control unit, by sampling VCC, storing and computing, draws inductive current, and when inductive current is more than VTH when, comparator output reset signal to latch, latch output shutdown signal closes power MOS pipe.The lowest point computing unit includes, sampling hold circuit, and the lowest point counting circuit.The lowest point computing unit sampling, the lowest point signal of storage metal-oxide-semiconductor drain electrode, to guarantee to be again turned on metal-oxide-semiconductor at the lowest point.
The invention have the advantage that the optimization by application framework, decrease the port number of LED current constant control, thus be greatly reduced system cost；Further, since eliminate the port of sensitivity, the noise immunity ability of whole scheme is made to be greatly improved.
Accompanying drawing explanation
Fig. 1 is common non-isolation type buck topology structure principle chart.
Fig. 2 is the internal control circuit of Fig. 1.
Fig. 3 is the improvement project of Fig. 1.
Fig. 4 is the schematic diagram of the present invention.
Fig. 5 is the internal control circuit figure of the present invention.
Fig. 6 is the implementation method of constant-current control unit.
Detailed description of the invention
The present invention uses the framework of uniqueness detect and control inductive current, makes whole application seem more simple in periphery, and ultimate principle is: the voltage at electric capacity two ends can not suddenly change, and is therefore fixed value within the KHZ clock cycle.VCC foot with CS for " " voltage seen, be the voltage on VCC electric capacity C10 and the linear superposition of pressure drop on CS detection resistance R14.By to the sampling of this voltage, difference, calculation process, inductive current i.e. can be controlled.
As shown in Figure 4, it is the overall framework figure of the present invention.Power stage includes power switch (being integrated in I3), inductance L0, sustained diode 0 and light emitting diode I0, I1, I2 etc..Inductive current detection resistance R0 mono-end is connected on CS, and the other end is connected on systematically GND；VCC electric capacity C1 mono-end is connected on VCC, and the other end is connected on systematically GND.The Same Name of Ends of drain terminal D and inductance L0 and the anode of sustained diode 0 of power MOS are connected together, the other end of inductance L0 is connected on one end of light emitting diode I0, I1, I2, the negative terminal of diode D0 is connected together with the light emitting diode other end, and is connected on together on output line voltage.
As it is shown in figure 5, controlling organization mainly includes the inductive current detection resistance R14 and VCC electric capacity C10 of the constant-current control unit in dotted line frame and the lowest point computing unit and periphery.Constant-current control unit includes, sampling keeps I32, difference and unit gain I25, comparator I26 and latch I27.The loop that current constant control is mainly formed by constant-current control unit, power tube M1, inductive current detection resistance R14, VCC electric capacity C10 realizes.When M1 opens when, inductance L6 is electrically charged, and inductive current persistently increases, and the pressure drop at R14 two ends also increases.Because VCC=V (C10)-V (R14), wherein V (device) refers to the pressure drop at these device two ends, so VCC voltage will constantly decline.Write down the VCC voltage of inductance peak value moment, be designated as VCC1；When power switch M1 closes when, R14 pressure drop is 0, writes down VCC voltage now, is designated as VCC0.VCC0-VCC1 is the crest voltage at R14 two ends, has controlled this voltage and has just controlled the electric current of light emitting diode I35.The lowest point computing unit, keeps I30, the lowest point to calculate I32 and latch I27 including sampling.Sampling keeps I30 to sample drain terminal signal, and stores the signal voltage under various state；The lowest point computing unit I32 to sampling keep I30 output be analyzed and calculate, draw the moment that the lowest point occurs, and send set signal to latch I27, latch I27 export high level signal open power tube M1.
Fig. 6 gives the one of constant-current control unit and is embodied as circuit.Described sampling keeps I32 to include sampling switch S1 and sampling capacitance C11.VCC voltage signal is stored on C11 electric capacity.Difference and unit gain I25 include metal-oxide-semiconductor M0, M1, M2, M3, M4, M5 and resistance R0, R1, R2 and current source I1.Before and after VCC, the signal in moment is after difference and unit gain I25 process, and restores inductive current and detect ohmically pressure drop (R14, such as Fig. 5) on resistance R2.Described comparator I26 includes metal-oxide-semiconductor M6, M7, M8, M9, M10 and resistance R3, R4 and current source I2, I3.When inductive current more than threshold value VTH when, error signal will be amplified by M10, and input reset signal to latch (described I27, Fig. 5), control inductive current with this.
Being presented above the concrete methods of realizing of the present invention, the detailed description of the invention of the present invention is a lot: as inductance element is changed to transformer element；Comparator is changed to integrator；Difference and unit increase unit and are transformed to trsanscondutance amplifier；Sample holding unit and integrator unite two into one；Sampling holding changes over other equivalent circuit forms etc..
The invention have the characteristics that
1 present invention, in the case of directly not detecting inductive current, achieves the control to inductive current indirectly；
2 present invention, in the case of the most directly detection the lowest point signal, indirectly achieve and distinguish the lowest point signal and extract.
Claims (4)
1. a control technique for switch power supply, inductance and current, including realizing the power stage of power management and conversion,
The current sense resistor (R14) of detection inductive current, the voltage detected when current sense resistor reaches to compare
During threshold value VTH of device, R14 both end voltage keeps the process of I23, difference and unit gain I25 through over-sampling,
Being reduced out, and be imported into the input of comparator I26, comparator will export reset signal to next
Level circuit.The reset terminal of latch I27 received by the outfan of I26, and power received by the outfan of latch I27
The control end of pipe M1.Reset signal will close power tube, and make the charging process of inductance L6 terminate.With this
Control inductive current.
2. control technique for switch power supply, inductance and current as claimed in claim 1, is characterized in that: described power
Level includes power switch (M1), one or more light emitting diodes and the inductance (L6) being sequentially connected with,
Also include the fly-wheel diode (D5) with light emitting diode and inductance (L6) reverse parallel connection, described light-emitting diodes
Pipe and inductance (L6) connect.
3. control technique for switch power supply, inductance and current as claimed in claim 1, is characterized in that: inductive current
The pressure drop of detection resistance is arrived by constant-current control unit indirect detection, and constant-current control unit is protected by sampling
Hold, the computing of the module such as difference and unit gain, restore the pressure drop at inductive current detection resistance two ends, from
And the pin of the least outside, make system work the most reliable.
4. control technique for switch power supply, inductance and current as claimed in claim 3, is characterized in that: inductive current
Determined by the lowest point computing unit during the beginning of charge cycle next time.Reset signal is received at power switch,
And after closing power switch pipe, inductance L6 enters the process of demagnetization.The lowest point computing unit is comprised
Sampling keeps I30 unit, samples the drain terminal voltage of power switch and preserves the voltage at crucial moment and believes
Breath；The lowest point computing unit calculates the lowest point due according to these information of voltage, and it is defeated to export set signal
Entering the reset terminal to latch, power tube opened by latch.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201510411484.3A CN106329911A (en) | 2015-07-09 | 2015-07-09 | VCC voltage detection-based three-terminal constant current control framework of switching power supply |
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| CN201510411484.3A CN106329911A (en) | 2015-07-09 | 2015-07-09 | VCC voltage detection-based three-terminal constant current control framework of switching power supply |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114977741A (en) * | 2022-06-06 | 2022-08-30 | 北京芯格诺微电子有限公司 | Switching period self-adaptive control method applied to switching power supply |
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2015
- 2015-07-09 CN CN201510411484.3A patent/CN106329911A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114977741A (en) * | 2022-06-06 | 2022-08-30 | 北京芯格诺微电子有限公司 | Switching period self-adaptive control method applied to switching power supply |
| CN114977741B (en) * | 2022-06-06 | 2023-05-26 | 北京芯格诺微电子有限公司 | Switching period self-adaptive control method applied to switching power supply |
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